<!DOCTYPE html>
<html lang="en">
<head>
  <meta charset="UTF-8">
  <meta name="viewport" content="width=device-width, initial-scale=1.0">
  <title>Document</title>
</head>
<body>
  <div id="app">app</div>

  <script src="https://unpkg.com/react@16/umd/react.development.js" crossorigin></script>
  <script src="https://unpkg.com/react-dom@16/umd/react-dom.development.js" crossorigin></script>
  <script src="https://unpkg.com/babel-standalone@6/babel.min.js" crossorigin></script>

  <script type="text/babel">
    
    class App extends React.Component {
      constructor(props) {
        super(props)

        this.state = {
          
        }
      }

      render() {
        var elementObj = (
          <div>
            <div className="header">
              <h1 title="标题">标题</h1>
            </div>
            <div className="content">
              <h1 title="内容">内容</h1>
              <button className="btn" style={{color: 'red'}}>按钮</button>
            </div>
          </div>
        )
        
        console.log(elementObj)

        return elementObj
      }
    }

    ReactDOM.render(<App />, document.getElementById('app'))
  </script>
</body>
</html>